[build.zig] Override config.h definitions

[lnc3l0t]

Overview

This PR introduces a new option allowing build.zig to override config.h settings using a simple string:

pub fn build(b: *std.Build) !void {
// ...
const config: []const u8 =
    "-DSUPPORT_FILEFORMAT_JPG -DSUPPORT_FILEFORMAT_PNG=0";

const raylib_dep = b.dependency("raylib", .{ .config = config });
// ...
}

This example enables support for the JPG format (disabled by default) and disables support for the PNG (enabled by default).

Two commits are present in the PR:

• the first allows for all definitions in config.h to be overriden, it has more cumbersome parsing since some definitions have different data types
• the second restricts the user to override only SUPPORT_* flags (which simplifies the implementation and you could possibly merge, given my assumptions are correct [below]).

Thoughts

• Issue [build] Support config header in build.zig #3516 suggested the addConfigHeader function, but I haven't found a way to use it. My logic mimics what has been done for CMake: parse config.h to retrieve default values and override them with the ones provided by user, then inhibit config.h by supplying -DEXTERNAL_CONFIG_FLAGS
• In CMake for what I can gather only the SUPPORT flags are handled, therefore my second commit (99307a4). I was thinking that after -DEXTERNAL_CONFIG_FLAGS all the other flags wouldn't be set, but it seems everything is redefined if needed in the various source file (is this assumption correct?).

I used a command to find references to all NON-SUPPORT flags (all are redefined elsewhere except CONFIG_H)

> cat src/config.h | grep -Eo "^#define \w+" | cut -d" " -f2 | grep --invert SUPPORT | parallel --tag grep -Erni \"#define {}\" --exclude=config.h --before-context=1 \| wc -l | column -t
CONFIG_H                                     0
MAX_FILEPATH_CAPACITY                        2
MAX_FILEPATH_LENGTH                          4
MAX_KEYBOARD_KEYS                            2
MAX_MOUSE_BUTTONS                            2
MAX_GAMEPADS                                 2
MAX_GAMEPAD_BUTTONS                          2
MAX_GAMEPAD_AXIS                             2
MAX_GAMEPAD_VIBRATION_TIME                   2
MAX_CHAR_PRESSED_QUEUE                       2
MAX_TOUCH_POINTS                             8
MAX_KEY_PRESSED_QUEUE                        2
MAX_AUTOMATION_EVENTS                        2
MAX_DECOMPRESSION_SIZE                       2
RL_DEFAULT_BATCH_BUFFERS                     8
RL_DEFAULT_BATCH_DRAWCALLS                   8
RL_DEFAULT_BATCH_MAX_TEXTURE_UNITS           8
RL_MAX_MATRIX_STACK_SIZE                     8
RL_MAX_SHADER_LOCATIONS                      8
RL_CULL_DISTANCE_NEAR                        8
RL_CULL_DISTANCE_FAR                         8
RL_DEFAULT_SHADER_ATTRIB_LOCATION_POSITION   2
RL_DEFAULT_SHADER_ATTRIB_LOCATION_TEXCOORD   5
RL_DEFAULT_SHADER_ATTRIB_LOCATION_NORMAL     2
RL_DEFAULT_SHADER_ATTRIB_LOCATION_COLOR      2
RL_DEFAULT_SHADER_ATTRIB_LOCATION_TEXCOORD2  2
RL_DEFAULT_SHADER_ATTRIB_LOCATION_TANGENT    2
RL_DEFAULT_SHADER_ATTRIB_NAME_POSITION       5
RL_DEFAULT_SHADER_ATTRIB_NAME_TEXCOORD       11
RL_DEFAULT_SHADER_ATTRIB_NAME_NORMAL         5
RL_DEFAULT_SHADER_ATTRIB_NAME_COLOR          5
RL_DEFAULT_SHADER_ATTRIB_NAME_TANGENT        5
RL_DEFAULT_SHADER_ATTRIB_NAME_TEXCOORD2      5
RL_DEFAULT_SHADER_UNIFORM_NAME_VIEW          5
RL_DEFAULT_SHADER_UNIFORM_NAME_PROJECTION    5
RL_DEFAULT_SHADER_UNIFORM_NAME_MVP           5
RL_DEFAULT_SHADER_UNIFORM_NAME_NORMAL        5
RL_DEFAULT_SHADER_UNIFORM_NAME_MODEL         5
RL_DEFAULT_SHADER_UNIFORM_NAME_COLOR         5
RL_DEFAULT_SHADER_SAMPLER2D_NAME_TEXTURE0    5
RL_DEFAULT_SHADER_SAMPLER2D_NAME_TEXTURE1    5
RL_DEFAULT_SHADER_SAMPLER2D_NAME_TEXTURE2    5
MAX_TEXT_BUFFER_LENGTH                       5
SPLINE_SEGMENT_DIVISIONS                     2
MAX_TEXTSPLIT_COUNT                          5
MAX_MATERIAL_MAPS                            2
MAX_MESH_VERTEX_BUFFERS                      2
AUDIO_DEVICE_FORMAT                          2
AUDIO_DEVICE_SAMPLE_RATE                     2
AUDIO_DEVICE_CHANNELS                        2
MAX_AUDIO_BUFFER_POOL_CHANNELS               2
MAX_TRACELOG_MSG_LENGTH                      2

• Zig doesn't have a standard regex support, the parsing is done manually in my code
• In the second commit I added lines to trim whitespace, they are not really needed given the current state of config.h should I remove them? and assume the formatting will always be the same
• Should I remove the comments?
• I think after we decide the correct implementation I will have to rebase the commits to have a single one

Thank you for considering my PR :)

[Gamer-Kold]

Looks good to me

[Gamer-Kold]

As for the questions about the implementation that you have I am not the person to answer them.

But I can confirm that the implementation is doing what you're saying its doing. I think as a user of the build.zig; I'd like some comments explaining that it only works for the SUPPORT flags.

[lnc3l0t]

First commit (4da7f82) makes it possible to configure everything, not just the SUPPORT flags.
I don't know if you'd want to test it, but thanks for the feedback @Gamer-Kold

[raysan5]

@lnc3l0t I'm merging it but note that I can not verify this PR.